Nonmetal carbides

ELEMENTS (Metals and intermetallic alloys metalloids and nonmetals carbides, silicides, nitrides, phosphides)... 

ELEMENTS (Metals and intermetallic alloys metalloids and nonmetals carbides, silicides, nitrides, phosphides) l.A Metals and Intermetallic Alloys l.AA. Copper-cupalite family TAB. Zinc-brass family l.AC. Indium-tin family l.AD. Mercury-amalgam family l.AE. Iron-chromium family l.AF. Platinum group elements l.AG. PGE-metal alloys... 

Chlorine Ammonia, acetylene, alcohols, alkanes, benzene, butadiene, carbon disulflde, dibutyl phthalate, ethers, fluorine, glycerol, hydrocarbons, hydrogen, sodium carbide, flnely divided metals, metal acetylides and carbides, nitrogen compounds, nonmetals, nonmetal hydrides, phosphorus compounds, polychlorobi-phenyl, silicones, steel, sulfldes, synthetic rubber, turpentine... 

Lead dioxide Aluminum carbide, hydrogen peroxide, hydrogen sulfide, hydroxylamine, ni-troalkanes, nitrogen compounds, nonmetal halides, peroxoformic acid, phosphorus, phosphorus trichloride, potassium, sulfur, sulfur dioxide, sulfides, tungsten, zirconium... 

The crystal stmeture and stoichiometry of these materials is determined from two contributions, geometric and electronic. The geometric factor is an empirical one (8) simple interstitial carbides, nitrides, borides, and hydrides are formed for small ratios of nonmetal to metal radii, eg, < 0.59. 

Hardness (qv), which determines the resistance of a material to abrasion and deformation, is affected not only by composition but also by porosity and microstmcture. Higher cobalt content and larger carbide grain size reduce hardness and abrasion resistance but iacrease the toughness of cemented carbides. The trade-off of abrasion resistance and toughness enables the cemented carbide manufacturer to tailor these materials to a wide variety of metal-cutting and nonmetal-cutting appHcations. 

Cemented carbides play a cmcial role in the recovery of metallic ores and nonmetals by underground or open-pit mining practices, recovery of minerals such as coal (qv), potash, and trona, and drilling for oh and gas. The methods of excavation can be broadly classified into three types rotary... 

Cemented carbide iaserts and tools for metal-cutting and metal-working have traditionally accounted for the largest percentage of carbide iadustry sales. However, carbide tool consumption ia nonmetal-working fields, notably ia the constmction and transportation iadustries, has grown rapidly. On the other hand, the demand for primary materials has been somewhat reduced by use of recycled cemented carbide scrap. 

Complex Carbides. Complex carbides are ternary or quaternary intermetaUic phases containing carbon and two or more metals. One metal can be a refractory transition metal the second may be a metal from the iron or A-groups. Nonmetals can also be incorporated. 

Complex carbides are very numerous. Many newer compounds of this class have been discovered and their stmctures elucidated (20). The octahedron M C is typical where the metals arrange around a central carbon atom. The octahedra may be coimected via corners, edges, or faces. Trigonal prismatic polyhedra also occur. Defining T as transition metal and M as metal or main group nonmetal, the complex carbides can be classified as (/)... 

Whereas finely divided cobalt is pyrophoric, the metal in massive form is not readily attacked by air or water or temperatures below approximately 300°C. Above 300°C, cobalt is oxidized by air. Cobalt combines readily with the halogens to form haUdes and with most of the other nonmetals when heated or in the molten state. Although it does not combine direcdy with nitrogen, cobalt decomposes ammonia at elevated temperatures to form a nitride, and reacts with carbon monoxide above 225°C to form the carbide C02C. Cobalt forms intermetallic compounds with many metals, such as Al, Cr, Mo,... 

Carbon forms ionic carbides with the metals of Groups 1 and 2, covalent carbides with nonmetals, and interstitial carbides with d-block metals. Silicon compounds are more reactive than carbon compounds. They can act as Lewis acids. 

Like the carbides, they allow nonmetal vacancies (i.e., nitrogen) in the lattice. 

Solution behavior and phase equilibria are published for ternary and higher order t phases and for the mixed interstitial r-carboborides (boro-carbides) with extended substitution on both the metal and nonmetal sublattices ... 

As we shall see later, borides (as well as oxides, nitrides, carbides, etc.) react with water to produce a hydrogen compound of the nonmetal. Thus, the reaction of magnesium boride with water might be expected to produce BH3, borane, but instead the product is B2ff6, diborane (m.p. -165.5 °C, b.p. -92.5 °C). This interesting covalent hydride has the structure... 

Cement copper, 7 688 Cemented carbides, 4 655-674, 693 25 359 economic aspects, 4 672 metal-cutting applications, 4 662-670 nonmetal-cutting applications,... 

Vanadium combines with other nonmetals at elevated temperatures forming binary compounds. Such compounds include nitride, VN carbide VC, and the sulfides, VS (or V2S2), V2S3, and V2S5. 

The crystal structure and stoichiometry of these materials is determined from two contributions, geometric and electronic. The geometric factor is an empirical one (8) simple interstitial carbides, nitrides, borides, and hydrides are formed for small ratios of nonmetal to metal radii, eg, rx / rM < 0.59. When this ratio is larger than 0.59, as in the Group 7—10 metals, the structure becomes more complex to compensate for the loss of metal—metal interactions. Although there are minor exceptions, the H gg rule provides a useful basis for predicting structure. 

Why do carbides and nitrides exhibit the properties that make them so useful in industrial applications It is well accepted that these properties are related to the strength of interatomic bonding.2 In transition metal carbides and nitrides, bonding is believed to have both covalent and ionic contributions.3 The carbon or nitrogen atoms occupy interstitial sites in the metal lattice and are believed to promote strong metal-to-nonmetal and metal-to-metal bonds.1 More detailed bonding explanations require... 

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